N‐Heterocyclic Carbene Analogues of Nucleophilic Phosphinidene Transition Metal Complexes
Adinarayana Doddi, Dirk Bockfeld, Thomas Bannenberg, Matthias Tamm
Abstract
Abstract Chloride abstraction from the complexes [(η 6 ‐ p ‐cymene){(IDipp)P}MCl] ( 2 a , M=Ru; 2 b , M=Os) and [(η 5 ‐C 5 Me 5 ){(IDipp)P}IrCl] ( 3 b , IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene) with sodium tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate (NaBAr F ) in the presence of trimethylphosphine (PMe 3 ), 1,3,4,5‐tetramethylimidazolin‐2‐ylidene ( Me IMe) or carbon monoxide (CO) afforded the complexes [(η 6 ‐ p ‐cymene){(IDipp)P}M(PMe 3 )]BAr F ] ( 4 a , M=Ru; 4 b , M=Os), [(η 6 ‐ p ‐cymene){(IDipp)P}Os( Me IMe)]BAr F ] ( 5 ) and [(η 5 ‐C 5 Me 5 ){(IDipp)P}IrL][BAr F ] ( 6 , L=PMe 3 ; 7 , L= Me IMe; 8 , L=CO). These cationic N‐heterocyclic carbene‐phosphinidene complexes feature very similar structural and spectroscopic properties as prototypic nucleophilic arylphosphinidene complexes such as low‐field 31 P NMR resonances and short metal‐phosphorus double bonds. Density functional theory (DFT) calculations reveal that the metal‐phosphorus bond can be described in terms of an interaction between a triplet [(IDipp)P] + cation and a triplet metal complex fragment ligand with highly covalent σ‐ and π‐contributions. Crystals of the C−H activated complex 9 were isolated from solutions containing the PMe 3 complex, and its formation can be rationalized by PMe 3 dissociation and formation of a putative 16‐electron intermediate [(η 5 ‐C 5 Me 5 )Ir{P(IDipp)}I][BAr F ], which undergoes C−H activation at one of the Dipp isopropyl groups and addition along the iridium‐phosphorus bond to afford an unusual η 3 ‐benzyl coordination mode.